Lead alloy



Jan. 31, 1939- B. JONES ET AL 2,145,513

LEAD ALLOY Original Filed Feb., 24, 19:57 2 sheets-sheet 1 Jan. 31, 1939. B. JONES ET AL I 2M5,513

LEAD ALLOY Original Filed Feb. 24, 1937 2 Sheets-Sheet 2 fly. 4.

I verv-rwe s RM 307 41% at a wan. w, m hu fi'w Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE 2,145,513 LEAD ALLOY Original application February 24, 1937, Serial No.

127,470. Divided and this application September 27, 1937, Serial No. 165,990. In Great Britain June 4, 1936 3 Claims.

This invention relates to alloys of lead and tellurium containing copper, and the present application is a division of our pending United States patent application Serial No. 127,470, filed February 24, 1937.

In British specification No. 414,606 are described alloys of this nature containing a proportion of from 0.01-0.1% of tellurium and 0.01- 0.15% of copper,.it being stated that the incorporation of the tellurium and the copper in the alloy conjointly imparts to the alloy a greater resistance to corrosion than an equivalent quantity of either of these elements separately.

We have now found that quite exceptional and unexpected properties are possessed by lead-tellurium alloys containing copper in a proportion of from 0.060.1%. When the copper is present in quantities contained within this narrow range a noticeable refinement in the crystal structure is observed in the cast condition, so.that even when the metal is subjected to burning, as during awelding operation, the development of a coarse structure is inhibited.

In the case of lead-tellurium-copper alloys in which the proportion of copper lies below the lower limit, there is a tendency for a. coarse structure to develop in a welded joint, and the existence of such a zone of coarse structure adjacent the fine structure of the body of the welded sheets constitutes a possible source of weakness. The development of such a coarse structure in the welded joints is, however, avoided when the proportion of copper exceeds 0.06%.

The lower limit of the copper content is a critical one, and even slightly below it (e. g. with a copper content of 0.05%), the inhibiting effect on-the development of a7 coarse structure in the weld disappears. The upper limit is less well defined. and a segregation of the excess copper content begins to take place as the copper content rises from 0.08% to 0.1%.

The invention will now be described in further detail with reference to the accompanying drawings, in which:-

Fig. 1 is a sketch made from a photomicrograph of an etched section showing magnified five times the crystalline structure in the cast state of a lead alloy containing 0.05% tellurium and 0.051% copper.

Fig. 2 is a similar view, at the same magnification, of the crystalline structure in the cast state of a lead alloy containing 0.05% tellurium and 0.067% copper.

Fig. 3 shows a photomicrograph of an etched section, the magnification being seven, through a welded joint between sheets of a lead alloy containing 0.05% tellurium but no copper.

Fig. 4 is a similar view, at the same magnification, of a welded joint between sheets of a lead alloy containing 0.05% tellurium and 0.067% copper.

Fig. 5 is a diagrammatic sectional view illustrating the segregation which occurs in a casting made from a lead alloy containing 0.05% tellurium and 0.08% copper.

The proportion of copper in alloys of lead, tellurium and copper, has a decisive effect on the.

size of the crystals in the cast condition. If the proportion of copper is below the critical limit of 0.06% the structure is coarse, as indicated in Fig. 1 which shows an alloy of which the copper content is 0.051%. Above 0.06% of copper, however, the structure of the metal is very noticeably refined, as is clearly indicated in Fig. 2 which shows an alloy of which the copper content is 0.067%.

This refinement of the crystal structure leads to important results in the application of the alloys to the manufacture of welded articles,

The subjection of the metal to the high temperatures involved in welding leads to the development of a coarse structure adjacent the Weld, and consequently weakness, when the copper content of the alloy is less than 0.06%. This is clearly to be seen in Fig. 3. Where, however, the copper content is above 0.06%, the fine structure persists even after welding, as shown in Fig. 4, with the result that a very much stronger joint is obtained.

Welding may be efiected in the usual manner, adding metal from a welding stick. The invention includes the use of a welding stick made from a copper-tellurium-lead alloy containing from 0.06-0.1% of copper and from 0.02-0.25% of tellurium for making welded joints between sheets of ordinary lead or of lead alloys. As some metal will in general melt from the body of the sheets as well as from the stick, the amount of copper in the stick should be sufficient to ensure that the copper concentration in the melt does not fall below 0.06%.

It is preferred to keep the copper content below 0.07%, as otherwise some tendency towards segregation is observed, as may be seen from Fig. 5, where the excess copper is indicated at A, having segregated to the top of the casting. It will be appreciated that this figure is diagrammatic only, the segregated copper being shown, for the sake of clarity, on a greatly enlarged scale. The copper content can, however, be increased to 0.1% without the effects of segregation becoming serious.

What we claim as our invention and desire to secure by Letters Patent is:-

1. A method of preparing from lead a welded article having a fine grained structure in the weld, which includes the steps of alloying the lead with from 0.02%-0.1% of tellurium and from 0.06%-0.1% of copper, forming separate members of the resultant alloy, and uniting such members by welding to form the article.

2. A method of making welded joints between members formed of lead or a. lead alloy to form a fine grained structure at the weld, which includes the step of fusing such members with a lead base alloy having such content of copper and tellurium, that the resultant weld will con- 

